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Monday, July 29, 2013

In Oracle Enterprise Linux 6.4 (OEL 6.4) 64-bit edition , the installation of vnc server package (RPM) is not very straight forward. In the blog post, we will explain about all the RPMs required for setup of vncserver utility in OEL 6.4

The vnc and vnc-server RPMs are not enough

1) Login as root

2) yum install vnc (installs tigervnc RPM)

3) yum install vnc-server (installs tigervnc-server-module RPM)

4) vncserver (Attempt to start vncserver service. But you will receive vncserver: command not found error message)

The vnc and vnc-server RPMs alone are not sufficient. You must also install tigervnc-server RPM explicity (the 3rd vnc server related RPM)

5) yum install tigervnc-server (This is the RPM that installs the vncserver utility in the path)

Conclusion

The yum utility seems to favor tigervnc software by default as it automatically downloads and installs tigervnc. As seen above, the number of RPMs needed for setting vncserver is not straightforward and you have to install the three RPMs above in that order.

Wednesday, July 17, 2013

You may encounter the "RMAN-06054: media recovery requesting unknown archived log ..."error when performing an incomplete database restore and recovery from an RMAN backup. This error is not a cause of concern under normal circumstances when you use the simple rman restore and recovery commands without a point-in-time recovery such as an UNTIL_TIME recovery.

This blog post assumes that you have already restored/recreated the spfile/pfile and control file respectively and now ready to execute the restore and recovery commmands.

Oracle does not stop the recovery at the last available archive log in the database backupsets as per the restored control file. Instead it keeps on requesting for the "next available archive log sequence" number. But in reality, as per the above example, there is no log sequence 3. So the database is already consistent after applying log sequence 2 (final archive log sequence as per the restored control file) and hence the recovery is in fact successful. Just try to open the database with the resetlogs option. It should work.

rman>exit
sqlplus '/ as sysdba'
sql>alter database open resetlogs
You should get the "Database altered" message which indicates that the database was opened successfully.

Conclusion

If you know about a command or option that lets rman automatically stop the recovery at the last archive log sequence in the backupset, then please comment on our post below. Such an option will help avoid getting the error in the first place.

Tuesday, July 16, 2013

One of the new features of Oracle 11g R2 is the RMAN backup-based duplication. One can clone an Oracle database using the source database backup without actually making a connection to it. This provides a traditional database cloning like experience (relying on just the backups alone) with the ease of RMAN. In this blog post, I want to write about certain points that you may not be aware of the backup-based duplication

RMAN configuration settings are not duplicated

If the source database has special RMAN configuration settings such as retention policy, archivelog deletion policy, controlfile autobackup etc., all these settings are reset (lost) in the duplicated database. So one has to manually enable these settings if one wants to retain them in the destination (new) database. This blog post assumes that one is not using the recovery catalog (catalog mode)

Source database

RMAN> show all;

using target database control file instead of recovery catalog

CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 5 DAYS;

CONFIGURE CONTROLFILE AUTOBACKUP ON;

CONFIGURE ARCHIVELOG DELETION POLICY TO BACKED UP 1 TIMES TO DISK;

Destination database (built using the backup-based duplication)

RMAN> show all;

CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default

CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default

CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default

Some init parameter values still contain source database references

If one uses a basic init parameter file for the destination database (to be duplicated database) that includes file system paths such as audit_file_dest,diagnostic_dest,utl_file_dir etc., then these are overwritten by the RMAN duplicate command with the spfile option and one may be suprised to see source database paths again in the destination database's init parameter file. One should not forget to update them manually with the correct destination file system paths.

After a successful backup-based duplication, one may be surprised to see a majority of the memory related initialization parameters containing two entries, one each containing the source database name and destination database name prefix. If that is the case, then one has to manually delete init parameters containing the source database name prefix. A below is one example

SOURCEDB.__db_cache_size=350000000

DESTDB.__db_cache_size=360000000

SOURCEDB.__java_pool_size=34567890

DESTDB.__java_pool_size=17534567

Also, a different matter is that the actual memory values are not exactly identical. One has to manually update the destination database init parameter values for memory if required.

Conclusion

The backup-based duplication is an excellent new feature in Oracle 11g R2 release for cloning databases. By following the above notes, one may avoid surprises after such a cloning exercise.

Monday, July 1, 2013

DBA University is offering an Oracle SQL PL/SQL online training course which runs on Sunday, Monday, Tuesday and Wednesday from 7 pm to 9 pm Central Time for a period of 7 weeks. Each training course runs for a period of 7 weeks for a total of approximately 56 hours with lots of remote lab practice. This course will help you provide expert level training in Oracle database with lot of practical exercises.

Introduction Have you seen your VNC Viewer showing a black screen intermittently ? We have a fix for it. This issue has been occurrin...

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